The present disclosure relates to an electrochemical cell system, and especially relates to the use internal reactant and fluid storage areas in a fully integrated electrochemical cell.
Electrochemical cells are energy conversion devices, usually classified as either electrolysis cells or fuel cells. An electrolysis cell functions as a hydrogen generator by electrolytically decomposing water to produce hydrogen and oxygen gases, and functions as a fuel cell by electrochemically reacting hydrogen with oxygen to generate electricity.
Referring to FIG. 1, a partial section of a typical proton exchange membrane fuel cell 10 is detailed. In fuel cell 10, hydrogen gas 12 and reactant water 14 are introduced to a hydrogen electrode (anode) 16, while oxygen gas 18 is introduced to an oxygen electrode (cathode) 20. The hydrogen gas 12 for fuel cell operation can originate from a pure hydrogen source, methanol or other hydrogen source. Hydrogen gas electrochemically reacts at anode 16 to produce hydrogen ions (protons) and electrons, wherein the electrons flow of from anode 16 through an electrically connected external load 21, and the protons migrate through a membrane 22 to cathode 20. At cathode 20, the protons and electrons react with the oxygen gas to form resultant water 14xe2x80x2, which additionally includes any reactant water 14 dragged through membrane 22 to cathode 20. The electrical potential across anode 16 and cathode 20 can be exploited to power an external load.
The same configuration as is depicted in FIG. 1 for a fuel cell is conventionally employed for electrolysis cells. In a typical anode feed water electrolysis cell (not shown), process water is fed into a cell on the side of theoxygen electrode (in an electrolytic cell, the anode) to form oxygen gas, electrons, and protons. The electrolytic reaction is facilitated by the positive terminal of a power source electrically connected to the anode and the negative terminal of the power source connected to a hydrogen electrode (in an electrolytic cell, the cathode). The oxygen gas and a portion of the process water exit the cell, while protons and water migrate across the proton exchange membrane to the cathode where hydrogen gas is formed. In a cathode feed electrolysis cell (not shown), process water is fed on the hydrogen electrode, and a portion of the water migrates from the cathode across the membrane to the anode where protons and oxygen gas are formed. A portion of the process water exits the cell at the cathode side without passing through the membrane. The protons migrate across the membrane to the cathode where hydrogen gas is formed.
The typical electrochemical cell system includes a number of individual cells arranged in a stack, with the working fluid directed through the cells via input and output conduits formed within the stack structure. The cells within the stack are sequentially arranged, each including a cathode, a proton exchange membrane, and an anode. In certain conventional arrangements, the anode, cathode, or both are gas diffusion electrodes that facilitate gas diffusion to the membrane. Each cathode/membrane/anode assembly (hereinafter xe2x80x9cmembrane electrode assemblyxe2x80x9d, or xe2x80x9cMEAxe2x80x9d) is typically supported on both sides by flow fields comprising screen packs or bipolar plates. Such flow fields facilitate fluid movement and membrane hydration and provide mechanical support for the MEA. Since a differential pressure often exists in the cells, compression pads or other compression means are often employed to maintain uniform compression in the cell active area, i.e., the electrodes, thereby maintaining intimate contact between flow fields and cell electrodes over long time periods.
Pumps are used to move the reactants and products to and from the electrochemical cell, which is connected to the liquid and gas storage devices by a system of pipes. This use of external pumps and storage areas both limits the ease with which electrochemical cells may be transported, and complicates the use of electrochemical cells in locations where pumps and storage tanks are difficult to introduce or operate.
While existing electrochemical cell systems are suitable for their intended purposes, there still remains a need for improvements, particularly regarding operation of electrochemical cell systems with minimal reliance on external pumps and storage units.
The above-described drawbacks and disadvantages are alleviated by an electrochemical cell system comprising at least one electrochemical cell provided in a vessel. The electrochemical cells each include a membrane electrode assembly having a first electrode, a second electrode, and a membrane disposed between and in intimate contact with the first electrode and the second electrode. The vessel is disposed around the membrane electrode assembly. The vessel defines at least a portion of a first storage area that is in fluid communication with the first electrode. Further vessel defines at least a portion of a second storage area that is in fluid communication with the second electrode.